lib: add bitrev8x4()

Add a function to reverse bytes within a 32 bit word.
Operate on a u32 rather than individual bytes.

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index fb790b8449c1..b97be27e5a85 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -29,6 +29,8 @@ static inline u32 __bitrev32(u32 x)
 
 #endif /* CONFIG_HAVE_ARCH_BITREVERSE */
 
+#define __bitrev8x4(x)  (__bitrev32(swab32(x)))
+
 #define __constant_bitrev32(x)  \
 ({                                      \
         u32 __x = x;                    \
@@ -50,6 +52,15 @@ static inline u32 __bitrev32(u32 x)
         __x;                                                            \
 })
 
+#define __constant_bitrev8x4(x) \
+({                      \
+        u32 __x = x;    \
+        __x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4);      \
+        __x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2);      \
+        __x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1);      \
+        __x;                                                            \
+})
+
 #define __constant_bitrev8(x)   \
 ({                                      \
         u8 __x = x;                     \
@@ -75,6 +86,14 @@ static inline u32 __bitrev32(u32 x)
         __bitrev16(__x);                                \
  })
 
+#define bitrev8x4(x) \
+({                      \
+        u32 __x = x;    \
+        __builtin_constant_p(__x) ?     \
+        __constant_bitrev8x4(__x) :                     \
+        __bitrev8x4(__x);                               \
+ })
+
 #define bitrev8(x) \
 ({                      \
         u8 __x = x;     \